Iran set up defensively frustrating La Roja, and could have come away with a famous draw had Saeid Ezatolahi's goal not been chalked off for being offside thanks to VAR.
Heading into the Group B game at the Mordovia Arena knowing they needed a win to secure their place in the Round of 16, the Iranians initially fell behind courtesy of a sublime strike from Ricardo Quaresma on the stroke of halftime.
It will, however, be no less of a shock if Iran manage victory over Portugal to send them through to the Last-16 for the first time in their history, and helping to deny Cristiano Ronaldo the trophy he so desperately craves.
Quaresma had never scored in a World Cup game; he had nine global goals in 78 previous appearances. Sign up for our month-long newsletter. One can watch the Iran v/s Portugal match on Jio TV and Airtel TV as well. Both matches will be streaming on TSN.ca. Team Melli showed plenty of spirit despite losing 1-0 to Spain.
What's at stake: Iran nearly certainly needs a win to advance to the knockout round. However, they could go through with a draw should Spain lose heavily to Morocco, as Fernando Hierro's side are on four points along with Portugal.
VAR had seen Portugal given a penalty of their own earlier in the contest. The Portuguese mastermind will be facing his native country as he aims to guide Iran through to the knockout stages.
Federation Internationale de Football Association world ranking: 37. Spain v/s Morocco will be Sony Ten 2, Sony Ten 2 HD, Sony Ten 3, Sony Ten 3 HD, Sony ESPN and Sony ESPN HD.
Spain will next face host Russian Federation on Sunday in Moscow.
Back to Group B and the matter in hand. ELO world ranking: 5.
Two draws and a win saw Portugal accumulate five points from their three games, and they have been involved in some of the tournament's most eye-catching moments so far. One of the Iranian fans, Mehdi Fayez, was reportedly messaged and told to present himself outside the hotel in a bid to improve Iran's chances by disrupting the Portugal team's peace.
The five-time Ballon d'Or victor is in red-hot form, scoring four in his first two games and coming off breaking the record for the most worldwide goals scored by a European player.
Meanwhile, Spain trailed 2-1 late to the group's cellar dweller, Morocco.